Transmembrane residues together with the amino terminus limit the response of the parathyroid hormone (PTH) 2 receptor to PTH-related peptide.
The mechanisms of ligand binding and receptor activation for G-protein-coupled receptors in the secretin/parathyroid hormone (PTH) receptor subfamily are not understood. The PTH1 receptor (PTH1R) signals in response to both PTH and parathyroid hormone-related peptide (PTHrP), whereas the PTH2 receptor (PTH2R) responds only to PTH, not to PTHrP. To locate PTHrP discriminatory domains in the PTH2R, we generated PTH1R/PTH2R chimeras in which the extracellular amino-terminal domains were exchanged. Production of cAMP in response to 1 microM PTHrP or PTH was identical in cells expressing the PTH1R with the PTH2R amino terminus and in cells expressing the PTH2R with the PTH1R amino terminus. The ability of the chimeric receptor with the PTH2R amino terminus to respond fully to PTHrP showed that the body of the PTH2R must contain sites that limit the response to PTHrP. Mutations to PTH1R sequence were therefore made in each of the seven transmembrane domains of the PTH2R. Mutations in transmembrane domains 3 and 7 resulted in receptors able to respond to PTHrP. Thus, residues in more than one domain form a barrier or filter, allowing the receptor to discriminate between different ligands.
Turner
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Endocrine Unit, Veterans Affairs Medical Center, San Francisco, California 94121, USA. pturner@itsa.ucsf.edu
Mefford
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Bambino
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Nissenson
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D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D003001:Cloning, Molecular; D000242:Cyclic AMP / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed / Q000235:genetics; D009893:Opossums; D010281:Parathyroid Hormone / Q000378:metabolism*; D044162:Parathyroid Hormone-Related Protein; D010446:Peptide Fragments / Q000378:metabolism*; D011506:Proteins; D044183:Receptor, Parathyroid Hormone, Type 2; D018016:Receptors, Parathyroid Hormone / Q000737:chemistry* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics*; D014162:Transfection / Q000235:genetics
D008565:Membrane Proteins; C470121:PTHLH protein, human; D010281:Parathyroid Hormone; D044162:Parathyroid Hormone-Related Protein; D010446:Peptide Fragments; D011506:Proteins; D044183:Receptor, Parathyroid Hormone, Type 2; D018016:Receptors, Parathyroid Hormone; D011993:Recombinant Fusion Proteins; C071784:parathyroid hormone-related protein (107-111); D000242:Cyclic AMP